In many cases, no. Most loft conversions on houses in England are permitted development, which means they can go ahead without a planning application as long as they stay within a set of national limits. But those limits are stricter than many people expect, some homes do not have permitted development rights at all, and the rules work differently in parts of Sussex.
This guide explains the national rules, when a dormer needs planning permission, the position with each council we work in, and how a Lawful Development Certificate gives you proof that your conversion is lawful.
Do you need planning permission for a loft conversion?
You do not need planning permission if the conversion counts as permitted development under Class B of the householder rules. The GOV.UK technical guidance on permitted development sets out the limits. The main ones are:
- Volume. The new roof space can be no more than 40 cubic metres larger than the original roof space on a terraced house, and no more than 50 cubic metres larger on a semi-detached or detached house. Any earlier roof extension counts towards that allowance.
- Height. No part of the work can be higher than the highest part of the existing roof.
- The front of the house. Nothing can extend beyond the plane of the roof slope that forms the main elevation and faces a road.
- Materials. The outside must look similar to the existing house.
- No balconies. Balconies, verandas and raised platforms are not permitted development.
- Side windows. Windows in a side wall or roof slope must be obscure-glazed and fixed shut, unless the opening part is more than 1.7 metres above the floor.
- Set back from the eaves. The enlargement should normally sit about 20 centimetres back from the original eaves.
If your plans go beyond any one of these, you need to apply for planning permission.
Do you need planning permission for a dormer loft conversion?
A rear dormer is often permitted development, provided it stays within the volume limit and the other conditions above. A dormer on a roof slope that faces the road is not, because it extends beyond the front roof plane, so it needs a planning application.
A dormer also needs planning permission, wherever it sits on the roof, if your home is in a conservation area or the South Downs National Park, or if an Article 4 direction has removed the relevant rights. More on both below.
Planning and the main types of loft conversion
- Rooflight conversions (often called Velux conversions) add windows to the existing roof slope without changing its shape. Rooflights fall under a separate class of permitted development and can project no more than 15 centimetres from the roof, so they rarely need planning permission.
- Dormer conversions are covered above. Rear dormers are usually permitted development within the limits. Front dormers need planning permission.
- Hip-to-gable conversions turn a sloping side of the roof into a vertical gable wall. On many semi-detached and detached houses this is permitted development, as long as the volume and other limits are met.
- Mansard conversions rebuild a roof slope at a much steeper angle. Because they change the roof so much, they usually need planning permission.
- L-shaped conversions combine a dormer on the main roof with one on the rear projection. The added volume can approach the limit, so the figures need checking at the design stage.
You can read more about each one in our guide to loft conversion types.
When permitted development does not apply
Some homes have no permitted development rights for a loft conversion, or have only some of them. The main cases are:
- Conservation areas and the National Park. Roof extensions are not permitted development in conservation areas, National Parks, National Landscapes or World Heritage Sites. Rooflights can still be possible.
- Article 4 directions. A council can use an Article 4 direction to remove specific permitted development rights in a defined area. Where that applies, work that would be permitted development elsewhere needs a planning application.
- Listed buildings. Any work that affects the character of a listed building needs listed building consent, whether or not it also needs planning permission.
- Flats and maisonettes. Householder permitted development rights apply to houses, so a loft conversion on a flat or maisonette needs planning permission.
- Conditions on earlier permissions. Some newer homes were built with conditions that remove permitted development rights. Your property’s planning history will show this.
Planning for loft conversions by council
We work across five district councils and the South Downs National Park. The national rules are the same everywhere, but local designations make a real difference to what needs an application.
Adur & Worthing
Adur & Worthing Councils run one shared planning service for Adur District, which includes Lancing, Shoreham-by-Sea, Southwick and Sompting, and for Worthing Borough. Both have conservation areas, so check whether your home sits in one before relying on permitted development. The built-up towns lie outside the National Park, which begins at the downland to the north.
Arun
Arun District Council handles planning for Littlehampton, Rustington, Angmering, East Preston and Ferring. The National Park boundary runs through Arundel, so homes there may fall under either authority depending on the address. Our Rustington loft conversions page covers the Arun position in more detail.
Brighton & Hove
Brighton & Hove City Council has an unusually high number of conservation areas, and Article 4 directions across parts of the city remove permitted development rights that a loft conversion would otherwise use. As a result, a rear dormer that would be permitted development in many other places often needs a full planning application here. The downland edges of the city lie inside the National Park. See our page on loft conversions in Brighton for more on the city.
Horsham
Horsham District Council handles planning for Storrington, Henfield, Steyning, Ashington and Cowfold. The southern part of the district along the Downs lies inside the National Park, and the boundary runs close to several villages, so it is worth confirming which authority covers your address.
Mid Sussex
Mid Sussex District Council handles planning for Burgess Hill, Hassocks and Hurstpierpoint. Burgess Hill sits well outside the National Park. The southern fringes of the villages nearer the Downs fall inside it.
South Downs National Park Authority
Inside the National Park, the South Downs National Park Authority is the planning authority, whichever district your home is in. Because the Park is protected land, roof extensions such as dormers are not permitted development there, so they need a planning application. Ditchling is one example of a village that lies wholly within the Park, and our Ditchling loft conversions page explains what that means in practice.
Lawful Development Certificates
If your loft conversion is permitted development, you can apply to the council for a Lawful Development Certificate. It confirms in writing that the work is lawful without planning permission. It is not a legal requirement, but it is a useful record. Buyers’ solicitors often ask for proof that a loft conversion did not need permission, and a certificate answers that question.
Apply before the work starts, with drawings that show the design meets the permitted development limits. The fee for a certificate for proposed work is half the fee for a planning application for the same work.
Our architectural partners can prepare the drawings and submit a Lawful Development Certificate application on your behalf, or a full planning application where one is needed.
Applying for planning permission
Where your conversion needs planning permission, the application goes to your council, or to the South Downs National Park Authority inside the Park. Most can be made online through the Planning Portal. A householder application includes drawings of the existing and proposed house, a site location plan and the application fee. Councils generally aim to decide householder applications within eight weeks of a valid submission.
The fee is set nationally and rises each April. Check the current figure on GOV.UK or the Planning Portal before you apply.
Many councils also offer pre-application advice. It is worth using in a conservation area, under an Article 4 direction or in the National Park, where the design will be looked at more closely. For how the approvals fit into the overall programme, see our guide to how long a loft conversion takes.
Building Regulations and party walls are separate
Planning permission and permitted development only answer whether you can build. Every loft conversion also has to meet Building Regulations, covering structure, fire safety, insulation and the staircase, and that approval is needed whether or not you need planning permission.
If your home shares a wall with a neighbour, the Party Wall etc. Act 1996 may apply. Party wall notices are the homeowner’s responsibility and are served by you or by a surveyor acting for you. A builder cannot serve them.
Please note: this guide is general information, not legal advice. Always confirm the planning position for your property with your local council or the South Downs National Park Authority before work starts, and discuss any party wall matters with a party wall surveyor.
Talk to us about your loft conversion
Apex Lofts & Construction designs and builds loft conversions across West Sussex and Brighton & Hove. We work with trusted architectural partners on the drawings, and they can prepare and submit a planning or Lawful Development Certificate application for you. Contact us to arrange a free site visit and talk through what your home allows. You can also see our full loft conversion service.